1. Field
The present disclosure relates to a digital-analog (D/A) converter, and more particularly, to a D/A converter including resistor elements for dividing voltages of a high potential power supply and a low potential power supply.
The development in digital technology has advanced digitalization of electrical appliances, such as audio equipment and video equipment. It is desirous that such an electrical appliance incorporate a D/A converter having higher operation speeds.
2. Description of the Related Art
FIG. 1 shows a conventional D/A converter 40 including voltage dividing resistor elements. The D/A converter 40 includes a voltage generation circuit 41, which is configured by sixteen resistor elements R, and a voltage selection circuit 42, which is configured by switch elements SW0 to SW15. The sixteen resistor elements R are set to have the same resistance value. Further, the sixteen resistor elements R are connected in series between a high potential power supply VRH and a low potential power supply VRL. The voltage generation circuit 41 equally divides the difference between the voltage of the high potential power supply VRH and the voltage of the low potential power supply VRL with the sixteen resistor elements R to generate divided voltages. Voltages V0 to V15 obtained by equally dividing the voltage difference between the high potential power supply VRH and the low potential power supply VRL are generated at nodes N0 to N15. The nodes N0 to N15 are defined by connection points of adjacent resistor elements R, a connection point between the low potential power supply VRL and its closest resistor element R, and a connection point between the high potential power supply VRH and the closest resistor R. The terminals of the resistor elements R that are closer to the low potential power supply VRL side, that is, the nodes N0 to N15, are respectively coupled to first terminals of the switch elements SW0 to SW15. The switch elements SW0 to SW15 have second terminals that are coupled to one another. The second terminals of the switch elements SW0 to SW15 are each coupled to an output terminal 44. The voltage selection circuit 42 is controlled by a control circuit 43. The control circuit 43 receives from an external device four bits of digital signals D0 to D3 representing a setting code. Then, the control circuit 43 decodes the digital signals D0 to D3, generates a control signal, and provides the control signal to the voltage selection circuit 42 to activate one of the switch elements SW0 to SW15.
The activated switch element couples one of the nodes N0 to N15 of the voltage generation circuit 41 to the output terminal 44. Therefore, voltage at a node N16 of the voltage selection circuit 42 is varied in accordance with the voltage at one of the nodes N0 to N15 coupled to the activated switch. In this manner, the D/A converter 40 outputs an analog signal AOUT having a voltage corresponding to the setting code (digital signals D0 to D3).
Japanese Laid-Open Patent Publication No. 4-506289 describes another example of a conventional D/A converter that includes ladder resistors and switches coupled to the output terminal side of the resistors.